Riverside Research Institute and the Division of Ultrasound in Columbia University's College of Physicians and Surgeons propose a collaborative effort to develop advanced clinical methods of ultrasonic tisse characterization for the thyroid, kidney, and liver. High-quality, clinical ultrasonic instrumentation will be combined with modern digital-computer technologies to acquire, analyze and display to the clinician data not provided by conventional ultrasonography. Analyses of data will provide spectral, cepstral, attenuation and other relevant measures of tissue characteristics for differential diagnosis of disease and for monitoring the efficacy of therapies. R.F. signals from ultrasonic echoes will be digitized and stored during data acquisition; these R.F. signals will be analyzed to provide unique tissue-characterization outputs complementary to the information provided by conventional methods. All digitized R.F. signals will be stored permanently and catalogued for the purpose of continued hypothesis formation and testing as experience accumulates and the data base expands. Computed tissue-characterization outputs also will be cataloged in a digital form along with linked lists of diagnostic, pathological, and other relevant medical data. Data will be obtained from the large volume of patients sent to the Division of Ultrasound for examination. In addition, tissues excised for medical reasons from patients previously examined will be studied in vitro. Engineering design and development (including all digital data-acquisition and processing routines) will be performed by RRI. Patient examinations and medical interpretation of data analyses will be performed by the Division of Ultrasound.